The present invention relates to semiconductor wafer processing and, particularly, to an apparatus for cleaning or otherwise processing a plurality of wafers positioned adjacent each other in a wafer carrier.
Semiconductor devices are typically fabricated on a circular semiconductor substrate called a wafer. Particulate matter present on the wafer surface during fabrication of the semiconductor device is problematic because particles present in active die areas of the wafer cause circuit defects. These defects result in nonfunctional electronic devices and increase the cost of semiconductor device production.
Conventional wafer surface cleaning systems use a cleaning solution in a tank coupled with a megasonic transducer to remove particulate matter from wafer surfaces. The wafers are typically vertically oriented in the tank and some parts of the wafer (and some wafers) are significantly farther way from the megasonic energy source than others. For example, the transducer may be positioned at the bottom of the tank. The result is a non-uniform cleaning rate from the bottom of the wafers to the top of the wafers. As wafers increase in size to accommodate larger circuits and increasing integration, the non-uniformity in cleaning rate increases in significance. Known systems attempt to correct this nonuniform effect by increasing processing time. Unfortunately, the increased processing time increases production costs. Similarly, other wafer processing systems, wherein wafers to be processed are held side-by-side in a wafer carrier or boat, also suffer from processing non-uniformity and decreased production efficiency.
Accordingly, there is a need for a wafer processing system wherein processing uniformity and processing time is improved without sacrificing process quality.